The development of siliceous cored armor is an attempt to provide for combat vehicles some measure of defense against shaped charges and HEP rounds without overburdening the tank with excessive weight or reducing its efficiency against conventional armor piercing ammunition. The capability of most materials for defeating shaped charges follows a so-called density law which states that the penetration of shaped charge jets is proportional to the square root of the shaped charge liner density divided by the square root of the target density. Consequently, on a weight basis, lighter targets are more advantageous than heavier targets. However, the use of massive quantities of low density material is not desirable for obvious design reasons. Therefore, the material desired is that which is an exception to this density law. The most noteworthy of these is glass. Under proper conditions, the stopping power of glass exceeds that of armor steel on a thickness basis and in many cases glass is more than twice as good as steel on a thickness basis. The development of siliceous cored armor is an effort to utilize this phenomenon of glass in a practical manner.